Micrometer



Oct. 14, 1952 s. G. ZUCKERMAN MICROMETER Filed Dec. 16, 1949 2 SHEETSSHEET l I 23 lmml inn-1?: l m4mmumuwuumuuwuvxwE IN EN O 3 E 53 27 5 SAMUEL GEORGE ZUOKERMAN FIG. 6. BY ATTORNEY Get. 14, 1952 5. cs. ZUCKERMAN 2,613,445

MICROMETER Filed Dec. 16. 1949 2 SHEETS-SHEET 2 IN VEN TOR SAMUEL GEORGE ZUCKERMAN ATTORNEY Patented Oct. 14, 1952 UNITED STATES PATENT oFF1,cE Y,-

2,613,445 MICROMETER Samuel George Zuckerman, New York, N. Y. Application December 16, 1949, Serial No. 133,226

This invention relates to micrometer calipers, particularly to direct reading micrometers.

The most widely used micrometer is the conventional screw type device in which the operative turning of the micrometer screw causes the contact face at the end of the spindle to move towards or away from the anvil, the rotary movement of the screw bearing a predetermined relation to the longitudinal movement of the spindle. Thus, in English measure micrometers, the customary pitch is .025, 'so that for each complete revolution of the screw there is a longitudinal spindle movement of .025", the scale on the barrel containing graduations of .025, and the beveled edge ofthe thimble rotatable about the barrel being graduated into25 parts, so that each graduation represents .001. To read a measurement, it is accordingly necessary to perform three steps, to wit, (1) take note of the highest figure visible on the barrel, (2) add .025

for each graduation visible between that figure and the thimble edge, and (3) add to this sum the number of the graduation on the thimble which coincides with or is nearest to the longitudinal reference line on the barrel.

Thus, with the conventional micrometer caliper, a number of operations are required which are not only time-consuming, but which render the readings subject to possible error. LYet', 'despite these shortcomings, this type of micrometer is preferred to any other known type, because of the inherent accuracy of the screw mechanism. In other words, it is only the rotary movement of the spindle which effects its operative longitudinal movement, without any intermediate moving elements to produce a cumulative sequence' of lost motions, such as by back-dash, inaccurate interfittings and progressive wear.

The various attempts to produce micrometers with direct-reading visual indicating means have met with no appreciable commercial acceptance.

Certain of these attempts have resulted in devices containing dials or pointers rotatably actuated by gearing disposed intermediate the rotatable spindle and the dial or pointer. While these devices have a field of use, they are not comparable in accuracy to the micrometer screw type, because of the intermediate gearing, and hence are not suitable for close work. Other direct-reading micrometers have had the required degree of accuracy, but only for a limited range,

enabling direct readings to be taken only for one or two turns of the spindle, beyond, which readings must be taken on anotherscale; 1 i. i

It is primarily within my contemplation to pro- 9 Claims. (C1. 33-166) vide amicrometer particularly, although not'exclusively, of the caliper category, which has all the advantages with respect to accuracy of the conventional screw micrometer, and yet which will give direct readings without the shortcomings of other direct-reading devices. More specifically, it is my objective to present a micrometer which will give direct readings, quickly and without the need to make any arithmeticalcomputations, which will have as wide a range as the conventional screw micrometer, which employs no intermediate gearing or other mechanism for controlling the longitudinalmovement of the spindle, and which willbe as convenient to han-.

dle as the conventional screw micrometer.

More specifically, itis an object of myinvention to employ a spindle containing threads thereon for controlling the longitudinal movement of p the spindle, and a longitudinal scale on abarrel,

substantially of the type used on conventional screw micrometers, but instead of the circum ferential scale on the beveled edge of the thimble (as in conventional structures), to employ. in

combination with the spindle a helical scale the length of which isjsufficiently great to enable a hundred graduations,each representing .001' in convenient and easily spaced arrangement. And

it is my object to provide, in combination with such a helical scale, special means; whichin themselves need not be fabricated with close tol' erances, to enable direct readings to be taken on the scale.

And in the last-mentioned aspect of my inven tion, it is a specific object to provide a rotary indicator, coactive with the said helical scale.

which will require negligible power for its opera tion, and which may have geared interconnecting means and play between associated "gear teeth, without affecting its 'accuracy.-

Still another object of my invention is -to pro-I vide a stationary vernier scale which willat'all times remain in close juxtaposition to its coactive' rotary scale actuated by the rotation o'ffthe spindle.

It is another object of myinventio t vide the aforesaid helical scale with "a helical groove serving the double function of separating the figures on adjacent convolutions of the scale, for clarity, and serving as a worm actuating means for the rotary indicator of my inveiitionf Still another object is to provide a guard serving the double function of protecting the'interiorj ofthe device against the infiltrationofdust; and serving as a finger support to prevent-"manual- .interference with the rotary operation of the device.

representingfour turns of the spindle H3. The calibrations on the helical scale 31 represent hundredths of an inch, there being onehundred such calibration lines on the helical length of four eonvolutions, a single convolution representing .025". The said calibrationstl on the barrel are thus multiples of the calibrations on scale 31. The wall 19 of the frame contains thereon th stationary vernier calibrations 62; and the adjacent terminal edge portion 63 contains thereon coacting calibrations, the relationship of the calibrations 62 and thoseon portion 63 being similarto conventional vernier calibrations and need not therefore be described. I

In the operation of this instrument, a measurement is taken of a selected object operatively disposed between the anvil l6 and the spindle l8 in the usual way. During the manual rotation of the thimble 26 and the concomitant rotation of the spindle l8, the indicating disc 46 is operatively rotated, in the manner indicated. This causes the indicating means, that is, the said dots on the disc to move through an are which is in intersecting relation to the directions of all the convolutions on the scale, the

diameter of the disc being no less than, and preferably greater (as illustrated) than the length of said helical scale 31 measured along its longitudinal axis. When the anvil l6 and spindle [6 are in operative contact with the object being measure, there will be one (or at most two) of the saiddots adjacent and in substantial longitudinal alignment with one (or at most two) of said convolutions, enabling a direct reading to be taken in the manner to be hereinafter set forth.

By referring to Figures 1 and 4, the setting for zero reading is illustrated. The reference edge 64 of the beveled portion 65 of the thimble 26 is directly on the zero line of th scale on barrel 3|; the reference edge 55 of plate 53 is coincident with the zeroline on convolution 56 of the helical scale; and only the zero calibra tion on stationary vernier scale 62 is in longitudinal alignment with a calibration line on vernier scale 63. It will also be noted that indicating dots 48 and 49 are both exposed to view, and opposite the extreme convolutions .(56 and 60), the readings on said convolutions, taken with reference to edge 55, both indicating no readings otherthan zero. The reading on barrel 3|, as aforesaid, indicates zero; and the reading on the vernier indicates zero; accordingly, the total reading is .0000".

When the setting is as shown inFigures 2 and 3, the reference edge 64 ofthe thimble. is in linewith the calibration marking .1. Indieating dot 52 is opposite convolution 56; and the reference edge 55, as well as the vernier readings, indicate zero as the reading on drum 33. Therefore, the exact Figure 4. is .1000". i

Figures 7 and 10, which illustrate another modiflcation to be hereinafter described, show other r in s which will help the understanding of this device- Referring to Figure 7, the reference line 55a is analogous to reference edge 55 01 the first form shown. The reference edge 64a of the thimble 26a is positionedbeyond the marking for .1". The reference dot'66 is positioned opposite the convolution 68, which merely means that the reading must be taken on that convolution. The reference line 55a .is disposed in line with reading .070; and the vernier reading indicates zero; Therefore, the reading for the setting of Figure}; is .l700' reading for the setting of 6 1 Referrin now to Figure 10, it will be seen that the reference edge 64a of the thimble 26a is disposed beyond the numeral .4 onthe barrel. The indicating dot 69 is disposed opposite convolution 61, thereby indicating that the reading must be taken on that convolution. The reference line 55a is positioned beyond calibration line .024 and the vernier indicates a .0002 reading, since a calibration marking on the rotary scale 70 of the vernier is in longitudinal alignment with the numeral 2 on the stationary portion H of the vernier. It is thus apparent that the direct reading, without any arithmetical computations, is .4242".

From the above description it will be seen that r all that need be done is torotate the thimble in conventional manner, until the spindle and anvil engage the object to be measured. The rotation of the spindle does two things; it causes the reference edge 64 (or 64a) of the thimble to move longitudinally along the barrel, and alsocauses the disc 46 to rotate, since the rotation of drum 33 produces a rotating of coacting gear 40 which carries the disc 46. Theaccuracy characteristic of the screw micrometer is inherent in this invention, since the longitudinal movement of reference edge 64 and therotary movement of drum 36 are controlled only by the accurate threads 21 which are capable of exceedingly close tolerances. There is no need for any undue accuracy with respect to the gear 40, 'since'this gear merely carries the indicator disc 46 which itself carries no scale nor points to a specific. marking on any scale. Thisdisc merely indicates where a reading is to be taken, and it matters not if there is a little play between the gear teeth, since that need only affect; the position of the, indicating dot with respect to a particular convolution. As long as the dot is opposite portionrof the convolution, it serves its intended purpose. It may be exactly on the medial line of the convolution, or somewhat to the right or left; but it will still indicate which convolution will give the reading. The only close tolerances that are required are in the screw thread 21, and in the pin and slot combination 35 and 36. Since the same tolerances that are applied in conventional screw micrometers can apply in the instant case,,this device will be as accurate as such conventional structures, in so far as the screw thread is concerned. As to the pin and groove tolerances, it is known that this type of construction permits of the closest possible accuracy. Experience has proven that with this particular construction, conventional fabricating methods will permit a tolerance of approximately .0003" between the pin and walls of the groove, and

this may amount to a possible error of one hundred thousandths of an inch, which is negligible.

Since the gear 46 and the disc 46 perform no work other than to bring the indicating dots to their proper positions, these elements may be made of light-weight material; and hence practically no load whatsoever is imposed upon the. instrument because of these elements.

It will furtherbe observed that the movable portion of the vernier is always adjacent the stationary portion, since the rotating drum does not; movein an'axial direction. This arrangement. assures easy and close reading of the vernier.

By referring to Figure 5 it .willrbe seen that the: rear of the instrument contains a guard member 12 attached to the frame l5; This servesa two-- fold purpose. In the firstplace, it seals the space "leading intotheinterior of the mechanism;

and in-the second place it'servesas a finger rest so that' in operatively holding the micrometen theguard and not the fingers will restagainst interfere with the barrel 33;

The form of my invention illustrated: in Figures 7 to 11 embodies substantially the constructionshown in Figures 1 to 6, except-that a trans parent windowconstruction -is-' added.

a substantially U-shaped plate i lis used,the

short leg 15 extending over the top a'ndrear of- Suitably secured to -the inside of the device. 7 the-plate'is the transparent sheet lti The aperture H in the plate exposes portion'of-th'e transparent sheet, toprovideawviridoW 78-for the drum 33a. Saidwindow' containsthereonthe reference line 5560 like the hairline on -a slide rule;

As-aforesaid, this line55a is analogous to reference edge 55 of the form first-abovedescribed. I

However, theportion 'mof the-window below reference line 55a exposes thelowenportionof the-drum 33a" to viewe- This makes it easierto effect the reading.

window 78, providing a dust-proof, yet readily visiblestructure. The aperture 80 ;formed4nthe wall of plate II, is analogous toaperture =54 of the first form described;

It will be observed that since-both formsof this invention embody; the-conventional elements of a spindle with .025" pitch threads'thereon, a thimble with beveled edge, a barrel, an internally threaded nut in engagement with the threadedportion of the spindle, theiabricatingequipmentnow used for making conventional micrometer screws maystill be-employedin-the manufacture of these basic components It is estimated that the additional components such as the frame, drum, gear, indicating disc and associated parts can be fabricated without great difiiculty and with conventional fabricating equipment. Ac-

cordingly,- the conversion of present micrometerfabricating plants to produce the presentdevice.

can be effectuated without excessive cost,

Inthe-above description, the invention has; been-disclosed merely by way of example and in preferred manner; but obviouslymany variations and-modifications may bemadetherein; It -'is to be understood, therefore, that the invention is not limited to any specific form or manner of practicing same, except in so far assuch limita-,.

tions are specified in the appendediolaims.

I claim:

1. In a micrometer of the class having a frame provided with an anvil, a calibrated barrel, a rotatable thimble and a spindle rotatable with the thimble and movable toward and away from the anvil, the combination of a helical scale member connected to and rotatably movable with said spindle, said scale member having a plurality of convolutions bearing scale calibrations thereon; rotatably mounted indicating means coactively rotatable with the spindle, a portion. of the arc' of rotation of said means being along a path in tersecting the directions of-all the convolutions" ofithechelical scale, and, a reference lineparallellto theaxis of the helical scale and extendingzaoross all the convolutions thereof.

2. In a micrometer of the class having a frame providedwith an anvil, a calibrated barrel, a rotatable thimbleand a spindle rotatable'with the thimble and movable toward and away from the anvil, the combination of ahelical scale memberconnected to and rotatably-movable withsaid spindle, saidscale member having plurality-of Furthermore, the entiredrum is completely sealed by the plate 'M an'd convolutions bearingscale 'calibrationswhereon, a reference lineparallel' to the axis of the helical scale and extending across all the-convolutionsthereof, androtatably mounted indicating means coactively rotatable withthe spindle, the portion of the arc of rotation-of said-means nearestsaid reference line being along a path'intersecting' the directions of; all the convolutions of the-helical scale.-

3: In a sorewm-icrometer, an anvil, a rotatable spindlemovable toward and away from the an vil, 1 a helical scale member connected to and rotatably movable with said spindle, 'a rotatably mountedindicating-disc* coactively rotatable with vthespindle,a peripheral portionof the disc-overlapping a portlon of the s'aidscaleya plurality of spaced indicating means-on the peripheral portion-ofthe disc, and a plateoverlying the disc; theplate having an apertured portion adjacent .the helical-scale',-the' diameter- 0f said disc being noless than-the lengthof said helical scalememper-measured along its longitud-inal'axis, whereby upon an operative; rotation of the disc the indi cating means-will move along an arcuate path intersecting the directions of all the convolutionsthe spindle, a peripheral-portion of the discoverlapping a portion of the said scale, and a plurality of-spaced indicating means on the peripheral portionof the disc, said'means comprisingimarkings so spaced: that the distance between adjacent markings measured-in a direction parallel-to" the axis of:the' helical scale member is substantially equaltothe median distance between theextreme opposite convolutions bearing tsaid :scale calibrations; andca plate overlying the'disc, the plate h'avin 'g an 'apertured portion adjacent the helical scale; the said apertured portion overlying a peripheralportion of'zthe disc-and being of a length at least equal .to .'the distance between the" twosaid extreme opposite convolutions; whereby two adjacentmarkings: may; be simultaneously exposed by said apertured portion-xv 5. In a screw micrometer, an anvil, a rotatable" spindle movable toward and away: from the am member connected to and:

vil, a helical scale rotatably movable with said spindle, a rotatably mounted: indicating thelspindle, 'a' peripheral portion of the disc overlappinga: portion of:the-said scale, a plurality of spaced indicating means'on the peripheral por tion or.the-disc, a plate overlying the disc, the plate: having an apertured 'portionadj aeent :the.

helical scale, the diameter of said .disc being. no

lessthan the lengthof said .helical'. scale member measured. along-its: longitudinal axis, whereby upon anoperative rotation .of the disc the-indieating: means: will move along; an arcuate path intersecting the directions :of all theconvolutions of ,the helical scaleythe said apertured portion overlyingia peripheral portion of the discito ex 6. a micrometer, thelcombination accordin toclaim' 5, said reference line'comprisingthe edge iof the said plate nearest the' helical; scale.

disc coactively rotatable with 7. In a micrometer, the combination according to claim 5, further provided with a transparent window disposed over the scale, and a line on said window constituting said reference line.

8. In a micrometer, the combination according to claim 5, said plate being of substantially U- shaped cross-section with one long and one relatively short leg, the said long leg overlying the disc, the said short leg being disposed behind said helical scale, the intermediate portion of the plate between said legs extending over the top of the scale, and a window in the plate disposed over a portion of the scale, said window having a line thereon constituting said reference line.

9. In a screw micrometer, an anvil, a rotatable spindle movable toward and away from the anvil, a drum mounted over the spindle, the spindle being in slidable engagement with the drum for longitudinal movement, connecting means between the drum and spindle, whereby they will rotate together, said drum having on the outer surface thereof a helical scale, a, rotatably mounted indicating disc coactively rotatable with the spindle, a peripheral portion of the disc overlapping a portion of the said scale, a plurality of spaced indicating means on the peripheral portion of the disc, a plate overlying the disc, the

plate having an apertured portion adjacent the helical scale, the diameter of said disc being no less than the length of said helical scale member measured along its longitudinal axis, whereby upon an operative rotation of the disc the indicating means will move along an arcuate path intersecting the directions of all the convolutions of the helical scale, the said apertured portion overlying a peripheral portion of the disc to expose the said indicating means when operatively adjacent the helical scale, and a reference line parallel to the axis of the helical scale and extending across all the convolutions thereof.

SAMUEL GEORGE ZUCKERMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

